1. Field of the Invention
The present invention relates to packing bags comprising overlaying films sealed together along the peripheral or circumferential portions of the films, and more particularly, to an improved seal-breaking structure for such packing bags.
2. Description of the Prior Art
Packing bags made by laying films one upon the other and sealing the peripheral or circumferential edge portions of the films are used in various fields. In order to access and utilize the contents of such packing bags, the packing bag must be opened by breaking the seal. A cutting tool or instrument such as scissors can be used for opening the packing bag, but it is desirable for convenience and utility to be able to tear open such packing bags by hand.
In the medical field, a commonly used orthopedic cast material is a water-curable cast material made by applying polyurethane polymer resin to a base fabric. This cast material hardens upon contact with the moisture present in the air and must therefore be held in a tightly sealed container such as in a film packing bag to avoid premature hardening. This cast material can furthermore contain a water-soluable tack-free agent such as a surface-active agent, ester of fatty acid, or the like which agent prevents the resin component of the cast material from adhering or sticking to the hands of a person, such as a physician or an orthopedic or cast technician, as the cast material is applied or wound around an injured or otherwise affected or diseased body part such as a limb or the like. However, a perfectly tack-free cast material cannot be realized, so that the cast technician or other applicator will wear gloves for the procedure in many cases. When such a cast material is placed or mounted onto an affected or a diseased body part, the cast material is taken out of the bag and is dipped into water, and is then wound around or otherwise applied to the diseased body part. As the cast material is handled using the thus wetted gloves, some of the tack-free agent and water will be present on the surface of the gloves. When the cast technician tries to open subsequent packing bags, the gloves will be quite slippery due to the water and the tack-free agent thereon making grasping and tearing open subsequent bags quite difficult. Numerous attempts have been made to provide a solution to this problem, for instance, reducing the thickness of the film used to make the packing bag so as to make the packing bag easier to tear. Another proposed solution is to use a material with a directional tear characteristic. Still another proposed solution is to increase the depth of the notch provided to facilitate the tearing of the packing bag. However, sufficiently satisfactory packing bags could not be obtained using such means without the undesirable result of lowering its durability.
Another alternative to facilitate the opening and seal breaking of such packing bags has been proposed by the present applicants wherein the bag structure is made in such a manner that, in at least one sealed peripheral or circumferential side of the packing bag, there is provided a notch, and also two or more holes extending through the bag adjacent two opposite sides of the notch. A user's fingers can be inserted and hooked in the holes to enable the user to grasp and tear open the packing bag, even when wearing wet gloves. One shortcoming of this alternative is the disposal of the tailings produced when the through holes are made in the bag. Another shortcoming is that the required manufacturing apparatus for the bag can be large and complicated. In addition, even to provide through holes of a size just sufficient for the finger to be inserted, it is necessary to make the width of the sealed peripheral portion more than 20 mm, resulting in lack of uniformity of sealing strength.
Another possible application for the present invention is in the field of packaging for foods, wherein various film packing bags made in such a manner that foodstuffs can be enclosed and sealed therein and be directly heated therein such as by boiling. This type of packing bag is also often handled by wet hands during food preparation and cooking. Furthermore, the packing bags themselves when removed from the boiling water after heating are also wet, and therefore difficult to open with hands which are wet and slippery so as to have a drawback similar to the shortcomings discussed above.